I have a 1995 BMW 730i. The car steering wheel shakes at 48-50 mph. There is no shake at any other speed and all the wheels have recently been balanced and checked for general damage. Any ideas?
I would inspect the tyres as TWR suggests. Have a feel around both sides of the tyres for lumps or bumps which would suggest the wire carcass is damaged.
I had this problem on one of my cars a few years ago, the noise and vibration at 40mph was unbelievable, but at 50mph it was fine. Investigating, we discovered a lump on the back of one of the rear tyres which could barely be seen but was easily detected by touch.